CODEWITHSUNDEEP
java-me
user1132732
user1132732

Reputation: 31

Why Java public API has private method?

I was looking at java.security.BasicPermission API the other day. Why does it have a private method?

private void readObject(ObjectInputStream s) readObject is called to restore the state of the BasicPermission from a stream.

Sorry, I wasn't clear about what I asked. The class is just an example. There are many of them in Java library. All of them are read|write Object method. When they designed this API, why would they add a private method that an application can't use?

Upvotes: 3

Views: 553

Answers (3)

Jon Skeet
Jon Skeet

Reputation: 1500065

readObject is a used by the Java serialization framework when deserializing, to provide support for custom operations. Unlike most private methods, it usually wouldn't be called within the class itself - instead it's called by the framework / JVM, which obviously violates normal expectations somewhat.

See the docs for Serializable for more details.

Upvotes: 3

Arindam
Arindam

Reputation: 342

A private method is a method that cannot be accessed by the API, but is used internally to do something.

For example, take a real world example like a Microwave. It would have external user inputs like bake(), heat(), etc ... but a private internal function like cookFor(Time minutes, Temperature t).

So now the Microwave implementation is really simple,

public void bake() {
  cookFor(45, 300);
}

public void heat() {
  cookFor(5, 100);
}

etc. The reason we have functions is to write good procedural programs, and the private/public descriptor is used to encapsulate the class.

Upvotes: 0

Tudor
Tudor

Reputation: 62439

That method is probably called internally by one of the other public methods and should not be the concern of the API user.

Upvotes: 1

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